It means “to make
less severe”. Therefore, it can be defined as “taking action to reduce the
effects of a hazard”.

2.
What is Landslide?

Landslide

Landslide may be
defined as the mass of rocks and debris move down a slope.

Debris flow is also
known as mudslide.

3.
Differentiate floods and droughts.

Drought

· Drought
refers to the prolonged dryness of weather due to lack of rainfall.

· It
is difficult to indicate the time of its onset and end.

4.
Differentiate Tornadoes and Cyclones.

Cyclones

· The
cyclones are the strongest winds generated by the meeting of the cold and warm
fronts in the centre of low-pressure systems.

· When
they are all formed over the sea and oceans they become violent due to the fact
that there are no barriers to check these winds.

Tornadoes

· Tornadoes
refer to the violently rotating columns of air.

· They
extend from a funnel shaped cumulonimbus doud to the earth.

· Their
width varies from a few meter to more than a 36 kilometer and it rotates at a
speed between 64 km and 509 km per hour.

IV.
Answer the following questions in detail

1.
What do you meant by disaster? Explain the natural and man made disaster.

The disasters are
broadly classified into Natural and Man- made. The natural disasters occur due
to the natural forces whereas the man-made disasters occur due to human
negligence, carelessness and ignorance.

2. Write about Tsunami and its effects on
environment.

Tsunamis

v They
are killer waves or Giant waves generated by earthquakes, volcanic eruptions or
underwater landslides.

v It
can raise to 15 metres or more in height. When earthquakes occur in the sea or
ocean, the sea waves rise to several meters and may reach the coast within a
few minutes.

v The
danger period of Tsunami can continue for many hours after a major earthquake.

v Tsunami
waves travel at a speed of 320 kilometer per hour and speed Increases when it approaches
the continents.

A killer Tsunami
hit South East Asian Countries on the 26th December of 2004 killing
more than 150000 lives.

v The
emotional, economic and ecological toll of the disaster cannot be calculated.
Many villages have lost entire generation.

v This
was the biggest earthquake to hit the world in 40 years.

v No
one could have thought that its effects would ripple worldwide overnight.

2. What are floods? List out the Mitigation
measures of flood affected areas.

Floods

v Floods
are a temporary inundation of overflow of water. They are caused due to very
heavy rainfall, cyclones, melting of snow, tsunami or a dam burst.

v Floods
are common features in Tamilnadu, Andhra Pradesh, and Orissa due to very heavy
rainfall during the Northeast Monsoon season and in Mumbai during the Southwest
Monsoon season.

v Floods
and droughts are the two problems caused due to the vagaries of monsoon.

Mitigation

v To
avoid overflow of water, many channels are required, to drain, especially near
the agricultural fields and low-lying areas.

v River
embankment, desilting are needed especially in the ponds and lakes.

v Sand
bags are to be kept in front of houses in the low-lying to block the water
reaching inside.

v Afforestation
is to b e encouraged to follow any one of the rain water harvesting methods.

v People
from the low-lying areas are to be shifted to elevated areas.

v Students
are to be trained to take part in the social activities at the time of floods.

3. What is called drought? Write about its
effects.

Drought

v Drought
refers to the prolonged dryness of weather due to lack of rainfall.

v It
is difficult to indicate the time of its onset and end. According to the Indian
Meteorological Department, the country is declared as drought-affected when
overall rainfall deficiency is more than 10 % over a long period.

v The
major reason for the drought is the scarcity of rainfall.

v Scarcity
of rain can be listed due to failure of monsoons, vagaries of monsoons,
deforestation, environmental degradation, high rate of evaporation, poor land
management, overgrazing and soil erosion.

v The
rainfed crops are mostly affected due to droughts.

v Other
effects are:

(i) scarce drinking
water supply,

(ii) shortage of
food,

(iii) lack of water
to the livestock,

(iv) nutrition
deficiency diseases and

(v) soil erosion.

4. Write about the seismic zones of India.

India is divided
into four seismic zones. They are listed in the following table: